Help with UV Mapping Islands
As you can see here, I have several texture materials. I'll convert everything just to a single texture.

First you will have to create a new 'UV Map'.
Now enter edit mode. See how my mesh is blurred and overlapping, just like yours.

With the new 'UV Map' selected, unfold the mesh using 'Smart UV Project'

Now in UV image editing mode, create a new texture where you will receive all textures. Opt for a resolution of 2048 or higher for better texture quality.
Now go to Scene> Bake> Bake mode and select 'Textures'

Click on bake and you will get all the textures of your character in that single image.
Now go to the Materials tab and delete all existing materials there, and create a new material.

Go to the texture tab and create a new texture and select the image you just created.
Everything is ready. All textures are rendered correctly.

Note that if any texture has alpha, it will lose transparency and will not have the expected result, as you can see in the hair and mustache.
I hope I have helped you and other people who are looking into this.